I can upload any files normally, but I can not download them.When I try to read the PDF file online,the explorer pop up the notice:

20140724011134.jpg (189.63 KiB) Viewed 4544 times

When I try to download any file by clicking the "Download" button, the explorer pop up the follow message. It tell me the file can't be found.

20140724001557.jpg (105.11 KiB) Viewed 4544 times

I have checked the MIME setting of the Apache and reinstalled the owncloud many times. I'm sure it doesn't have any wrong. But I can download all files by clicking the right button of mouse on the file names and "saved as ...", just can't download them by clicking the "download button" in the web GUI.

I want to know whether I ignored any permission setting which should be done?Thank you~!

In addition:I checked my logs by that way which RandolphCarter refered to. I set DEBUG to true and the loglevel to 0 in my config.php.

The follow is one log (/path/to/owncloud/data/owncloud.log):{"reqId":"53cfddba75d97","app":"PHP","message":"ob_end_clean(): failed to delete buffer. No buffer to delete at \/volume1\/web\/cloud\/lib\/private\/files\/view.php#205","level":0,"time":"2014-07-23T16:07:22+00:00","method":"GET","url":"\/cloud\/index.php\/apps\/files\/ajax\/download.php?files=Mini-XML__Version_2.5.pdf&dir=%2Fdocuments"}

PS：I have checked the MIME setting of the Apache and reinstalled the owncloud many times. I'm sure it doesn't have any wrong. But I can download all files by clicking the right button of mouse on the file names and "saved as ...", just can't download them by clicking the "download button" in the web GUI.

This problem has been resolved by myself by follow:Change the "data" folder path when I install the owncloud, from "/volume1/web/cloud/data" to "/var/service/web/cloud/data". (The "/var/service/web" is linked to "/volume1/web").

ah yes i remember there where similar posts about this on the Synology DS. This devices have a default X-Sendfile configured and you need to configure your vhost correctly according to this documentation: